Soap-filled dimethyldiphenylpolysiloxane grease



United States Patent O 3,544,464 SOAP-FILLED DIMETHYLDIPHENYLPOLY- SILOXANE GREASE Abraham L. Hajjar, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York No Drawing. Filed Sept. 25, 1969, Ser. No. 861,174 Int. Cl. C10m 7/48 US. Cl. 252-421 6 Claims ABSTRACT OF THE DISCLOSURE A grease composition containing a polysiloxane, the organic su'bstituents of which include phenyl and tetrachlorophenyl radicals in amounts of from to 50%, a higher fatty acid soap of lithium, an amount of a particular polyether sufiicient to cause the lithium soap of the fatty acid to disperse into the polysiloxane, and a suflicient amount of a base to render the grease alkaline. The grease is made by heating the polysiloxane, the polyether, the lithium soap of the higher fatty acid, and the base to a temperature of about 400 F. to 500 F., after which the grease composition is cooled to room temperature and milled. The grease composition is used in the journal bearings of starter motors having high current capacity and which run hot but are subjected to extremely low temperatures when not running.

CROSS-REFERENCES TO RELATED APPLICATIONS This invention is related to the invention described and claimed in the copending application of John H. Wright and Abraham L. Hajjar, Ser. No. 762,346, filed Sept. 16, 1968, for Methyl Silicone Grease Composition and Method of Making Same. That application describes a grease composition formed of organopolysiloxanes in combination with lithium soaps of higher fatty acids and a broad range of polyethers. However, it does not describe the criticality of the narrower range of polyethers useful in organopolysiloxane greases formed from phenyl and tetrachlorophenyl substitutes organopolysiloxane fluids.

BACKGROUND OF THE INVENTION The prior art has taught the formation of greases formed from organopolysiloxane fluids, including those using higher fatty acid soaps of lithium. While these soaps can be more easily milled into organopolysiloxane fluids having phenyl substituents, than into organopolysiloxane fluids having methyl substituents, even with the phenyl substituted organopolysiloxane fluids, there is significant formation of hard soap lumps during crystallization and these lumps are not dispersed during the milling process. This is true when less than about one-half of the substituents on the silicon are phenyl. Thus, when the grease is actually employed, there can be significant evaporation and bleed of the material. Additionally, the appearance of the grease, should the hard soap lumps not be adequately dispersed, is not acceptable.

The copending application of John H. Wright and myself, previously referred to, taught various materials for use in conjunction with the lithium soaps of higher fatty 3,544,464 Patented Dec. 1, 1970 acids and organopolysiloxanes substituted with methyl substituents. However, tests have indicated that this same range of polyethers cannot be employed when the fluid contains from 5 to 50% phenyl of tetrachlorophenyl substituents.

SUMMARY OF THE INVENTION In accordance with the present invention, 1 have discovered that a relatively narrow range of polyethers having the formula:

where R is a monovalent alkyl radical, preferably methyl, R is selected from the class consisting of phenyl and tetrachlorophenyl, b is from 0.05 to 0.5, and the sum of a and b is from 2.002 to 2.2. These fluids can have viscosities at 25 C. of from about 10 to 500 centistokes.

Employing certain of the polyethers set forth in the aforementioned copending application, soap lumps formed when employing fluids as described according to Formula 2 and these lumps did not disperse during the subsequent milling. Employing the particular polyethers of the present invention, as set forth in Formula 1, as the first soap crystals form, the polyether aids in wet ting them so that they are then able to attract additional fluid layers, additional soap layers, etc. The result is a soft grease, but with stability, having excellent appearance, and good bleed and evaporation properties. In the absence of the particular polyethers disclosed, it is im possible to adequately mill the grease composition.

It is thus an object of the present invention to provide a polyether process aid for use in combining the lithium soaps of higher fatty acids with organopolysiloxane fluids, having significant percentages of phenyl or tetrachloro phenyl substituents, to form a grease.

DESCRIPTION OF THE PREFERRED EMBODIMENTS where A is an alkyl substituent of from 1 to 14 carbon atoms, having up to one hydroxyl substituent, and n may vary from 4 to 2,000 in individual molecules, but has an average of from 20 to 40 as employed in the composition. I The alkyl radicals represented by A are those having from 1 to 14 carbon atoms, such as methyl, ethyl, butyl, hexyl, decyl, dodecyl, etc., and, preferably, includes the straight chain alkyls of this length. Up to one of the hydrogen substituents can be replaced by a hydroxyl substituent. As noted, the repeating polyether unit is the secpropylene oxide unit and the average number of repeating ether units in the chain is from 20 to 40. However, the polyethers employed are generally blends, and individual molecules in the blend can have an n value of between 4 and 2,000.

The polyether is employed in an amount of from 0.5 to 3 parts per 100 parts of the organopolysiloxane fluid. Preferably, the amount of polyether of Formula 1 which is employed is from 1 /2 to 3 parts per 100 parts of the organopolysiloxane fluid. If more than 3% is employed, various undesirable properties result in the grease, such as excessive odor. Less than about /2 part per 100 parts of the organopolysiloxane fluid results in an insuflicient amount to adequately wet the lithium soap of the higher fatty acid.

The fluid organopolysiloxane employed in the practice of the present invention are well known in the art. These fluids have the formula:

where R is a lower alkyl radical, preferably methyl, R is selected from the class consisting of phenyl and tetrachlorophenyl, b is from 0.05 to 0.5, and the sum of a and b is from 2.002 to 2.2. The viscosity of the particular fluid may vary from about 10 to 500 centistokes, when measured at 25 C.

It should be understood that the organopolysiloxane fluids of Formula 2 can include siloxane units of varied types and formulations, such as trimethylsiloxane units, dimethylsiloxane units, methylphenylsiloxane units, and monomethylsiloxane units. The only requirement is that the ratio of the various siloxane units employed be selected so that the average composition of the copolymeric fluid is within the scope of Formula 1.

While these various fluids can be used, the preferred fluid is formed of repeating or interspersed units of formulas:

CH: V (A) -i and (B) S i-O- JoHs or, in other words, dimethylsiloxane and diphenylsiloxane units. The particular order of these units within the chain of the fluid is not critical. The chain terminals on these polymers are, in general, trimethylsiloxy units.

The grease thickening agents employed in the present composition are well known in the art and include the lithium soaps of any of the higher fatty acids having from to 22 non-carboxyl carbon atoms. The term grease as employed herein is intended to refer to grease-like materials which may have consistencies varying from readily flowable materials to materials which exhibit essentially no flow. The consistency of the greases of the present invention depend upon the amount of thickening agent employed, the particular thickening agent employed, and the polysiloxane fluid employed in the grease. Examples of suitable thickening agents include the lithium soaps of higher fatty acids of 10 to 22 non-carboxyl carbon atoms such as lauric, myristic, palmitic, and stearic. Preferably, the soaps employed are lithium stearate and lithium myristate.

The amount of lithium soap employed in the grease of the present composition is not overly critical. However, it has been found that the amount of thickening agent should usually vary from about 8 to 40 parts, and preferably from about 20 to 25 parts, based on 100 parts of organopolysiloxane fluid.

In addition to the components described above, additives normally present in silicone greases can also be employed in the compositions of the present invention. Examples of such additivesinclude antioxidants such as amines, e.g., N-phenyl-alpha-naphthyl amine; corrosion inhibiters, e.g., zinc naphthanate; and extreme pressure additives, such as selenium disulfide, molybdenum disulfide, etc.

Further, as previously indicated a small amount of a base should be employed in an amount suflicient to maintain the grease at least slightly alkaline. A suitable base for use in this composition is lithium hydroxide.

In the preferred method of forming the grease of the present invention, the polysiloxane fluid, the lithium soap thickening agent, the polyether dispersing agent, and a small amount of a finely ground base such as lithium hydroxide, are heated to a temperature of about 400 F. to 500 F. Following this heating, the grease composition is cooled to room temperature and is then milled.

The following examples are illustrative of the practice of the present invention and are not intended for purposes of limitation.

EXAMPLE 1 In this example, a comparison was made between use of a polyether falling within Formula 1 and the use of other polyethers outside this formula. For convenience, the various materials are referred to in Table I by their trade names. Following Table I, a description of the various materials is set forth. In each case, a quantity of parts of a dimethyldiphenylpolysiloxane fluid was employed wherein approximately 10 weight percent of the fluid was constituted of diphenylsiloxane groups, and the viscosity at 25 C. was approximately 100 to centistokes. For each 100 parts of this fluid, 40 parts of lithium stearate and 5 parts of the process aid were used.

In each case, the components, including approximately 0.1% of lithium hydroxide, based upon the dimethylsiloxy diphenylsiloxy fluid, were thoroughly mixed and heated to approximately 450 F. The mixture was then cooled slowly, at about 1.2 F. per minute, to 350 F. at which point about 1.5% of N-phenyl-alpha-naphthyl amine, based upon the polysiloxane fluid, and an additional amount of the polysiloxane fluid, equal to parts, were added with continuous stirring. The slow cooling was continued and at 200 F. an additional 0.6% finely divided lithium hydroxide, based upon the total organopolysiloxane fluid, was added and the grease was cooled to room temperature, with continuous stirring. The grease formed was milled through a Morehouse mill three times. Processing with run 7 was extremely smooth with very few lumps due to lithium stearate conglomeration, while the other runs each showed significant lumps of the lithium soap during processing.

The structures of the materials referred to in Table 1 are as follows:

where n has an average value of 28. Thus, it can be seen that in the formulations set forth above, only the additive employed in run 7 :falls within the scope of the present invention. It was only in that run that the grease appearance prior to milling was even acceptable, thus indicating that the lithium soap had been dispersed and wet by the organopolysiloxane fluid, as desired. Further, it was the only composition of the runs referenced above, where the bleed and evaporation were not significantly increased, compared with the original composition lacking the particular polyether additive. While there is a slight amount of bleed, the difference between the bleed employing no polyether and the bleed with the polyether of the present invention is extremely significant.

Additionally, there were further problems when employing the polyethers of the other runs.'When, for example, the additive of run 2 was employed, there was great difficulty in pumping and handling the grease, during milling, because of the presence of large soap lumps. On the other hand, the composition of run 7 was easily pumped and milled with the conventional grease equipment, and there was a marked improvement in grease structure.

EXAMPLE 2 A further grease was formed in accordance with the present invention employing 100 parts of a dimethylsiloxydiphenylsiloxy organopolysiloxane having 40 weight percent diphenylsiloxy units and a viscosity of approximately 150 to 200 centistokes, when measured at 25 C. To this was added, in the same manner as in Example 1, 30 parts of lithium stearate, 4 parts of the polyether employed in run 7, and approximately 0.1 part of finely divided lithium hydroxide. During cooling of the material, an additional 100 parts of the organopolysiloxane fluid were added, along with 2 parts of N-phenyl-alphanaphthyl amine and, later, an additional 0.1 part of finely divided lithium hydroxide.

Processing was extremely smooth during the entire process, and very few lumps were noted during processing.

EXAMPLE 3 To a quantity of 100 parts of an of an organopolysiloxane fluid composed of dimethylsiloxy units and methyltetrachlorophenylsiloxy units, are added parts of lithium myristate, 1 part of a polyether having the formula:

and 0.1 part lithium hydroxide. The numeral 35 in the polyether formula above, represents an average number of propylene oxide units, and not the number of propylene units in each molecule in the polyether. The organopolysiloxane fluid has a viscosity of approximately 50 centistokes, when measured at 25 C., and there are approximately 10% tetrachlorophenyl units in the fluid, such that the designation b in Formula 2 is approximately 0.1, while R is methyl and R is tetrachlorophenyl. During coolingpf the mixture, an additional 100 parts of the rganopolysiloxane fluid is added along with an addition- 51 0.1 parts of lithium hydroxide. The milling is smooth and the finally formed grease has no discernible lumps.

Thus, a particular process aid, particularly, a polyether formed of recurring polypropylene units, with one alkoxy and'one hydroxy chain terminal, for use with organopolysiloxane fluids containing phenyl and tetrachlorophenyl substituents has been shown. While such a process aid additive is not required when the phenyl content is higher than that described, in the absence of such a process aid additive with the amounts of phenyl and tetrachlorophenyl substituents described, excessive lumps result during milling of the lithium soap of the higher fatty acid, such that the greases cannot be processed on standard equipment. Additionally, the appearance of the final grease is significantly improved employing these particular polyether additives, as are the bleed and evaporation of the final grease.

While the foregoing examples have illustrated certain embodiments of the present invention, it should be understood that our invention is broadly applicable to grease compositions containing polysiloxanes having alkyl and phenyl or tetrachlorophenyl substituents, in combination with a lithium soap of a higher fatty acid, and a polyether having only recurring polypropylene oxide units, along with a suflicient amount of base to maintain the composition alkaline.

What I claim as new and desire to secure by letters patent of the United States is:

1. A grease composition consisting essentially of:

(1) 100 parts of an organopolysiloxane fluid having a viscosity of from 10 to 500 centistokes of the average unit formula:

where R is a lower alkyl substituent, R is selected from the class consisting of phenyl and tetrachlorophenyl, the sum of a and b is from 2.002 to 2.2; and from about 5% to about 50% of the total number of R and R radicals are selected from the class consisting of phenyl and tetrachlorophenyl;

(2) from 8 to 40 parts of a grease thickening lithium soap of a fatty acid having from 10 to 22 non-carboxyl carbon atoms;

(3) from 0.5 to 3 parts of a polyether having the average formula:

where A is an alkyl substituent of from 1 to 14 carbon atoms with up to one hydroxyl substituent; n has a value of about 4 to about 2000, and the molecular weight of the polyether is from about 122 to about 180, 230; (4) a metal base in an amount suflicient to maintain the grease alkaline. 2. The grease composition of claim 1, wherein the polysiloxane fluid is formed of dimethylsiloxy units and dip enylsiloxy units.

6 3. The grease composition of claim 1, wherein the polyether is:

4. The grease composition of claim 1, wherein R is phenyl and R is methyl.

5. The grease composition of claim 1, wherein R is tetrachlorophenyl and R is methyl.

6. The grease composition of claim 1, wherein the poly- 15 ether is employed in an amount of from 1.5 to 3 parts.

References Cited UNITED STATES PATENTS 5/1954 Bidand 25228 6/1954 7 Hotten et a1 25242.1 7/1954 Zayac 25242.1 3/1959 Midland 252-29 FOREIGN PATENTS 7/1957 Great Britain. 7/ 1957 Great Britain.

IRVING VAUGHN, Primary Examiner US. Cl. X.R. 

